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Mitosis160-page7 - • Some microtubules from each pole of...

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Cell Reproduction: Mitosis - 7 Prophase Chromosome Condensation Duplicated chromosomes start to condense and tightly coil to become visible as threadlike structures as prophase starts. Chromosomes continue to condense and become thicker as prophase progresses. The nucleolus region (an aggregation of chromosome bits and concentrated RNA and protein) of the nucleus will disassociate. The duplicated chromosomes are firmly attached at their centromeres throughout the condensation and coiling. Nuclear membrane The nuclear membrane degrades in later prophase into small vesicles, which can be used to synthesis new nuclear membrane material in the new cells. Microtubule Organization Microtubules initiate spindle formation and determine the poles of the cell. The spindle apparatus will extend from the poles of the cell to the center of the cell surrounding the nuclear region and to the opposite pole of the cell.
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Unformatted text preview: • Some microtubules from each pole of the cell attach to each duplicated chromosome's kinetochores located in the centromere region. • Other microtubules overlap each other from the poles through the equator region of the cell. • In many cells, clusters of microtubules form around the centriole pairs, which replicated during interphase. Microtubules move centriole pairs to the respective poles of the dividing cell. These regions are sometimes called the asters. Centrioles are not essential to mitosis. Cells that lack centrioles still form the spindle complex. It's just a way to ensure that the new cells will have a pair of centrioles in their cytoplasm. Prophase Note: some researchers choose to call the events that include the degradation of the nuclear membrane and the attachment of the spindles to chromosomes prometaphase....
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